o 


U.S.  DEPARTMENT  OF  AGRICULTURE, 

BUREAU    OF   ENTUMOLOGY     CIRCULAR   No.  168. 

L.  O   HOWARD.  F-nlomologui  and  Chi^f  of  Bureau. 


SPRAYING   FOR  WHITE  PLIES 
IN  FLORIDA. 


BY 


\Y.  w.  MOTHERS, 
Entomological  Assistant. 


... 


•WaHTOH  iwnioin  >«,»T|»«  OTFKJ     <rw 


BUREAU  OF  ENTOMOLOGY. 

L.  O.  Howard.  Entomologist  and  Chief  of  Bureau. 
C.  L.  Mabxatt,  Entomologist  and  Acting  Chief  in  Absence  of  Chief. 
It.  S.  Clifton,  Executive  Assistant. 
W.  P.  Tastet,  Chief  Clerk. 
F.  H.  Chittenden,  in  charge  of  truck  crop  and  stored  product  inset  investigations, 
A.  D.  Hopkins,  in  charge  of  forest  insect  investigations. 
W.  D.  Hunteb,  in  charge  of  southern  field  crop  insect  investigations. 
F.  M.  Websteb,  in  charge  of  cereal  and  forage  insect  investigations. 
A.  L.  Quaintance,  in  charge  of  deciduous  fruit  insect  investigations. 
E.  F.  Phillips,  in  charge  of  bee  culture. 
D.  M.  Rogers,  in  charge  of  preventing  spread  of  moths,  field  icork. 

ROLLA  P.  CUBBIE,   in   charge  of  editorial   trork. 

Mabel  Colcord,  in  charge  of  library. 

ClTBUS  Fbuit  Insect  Investigations. 
C.  L.  M\ur. \n.  in  charge. 

R.   S.   WOGLUM,   W.    W.   YoTIIEBS.   E.   R.   S.ASSCER.  J.   R.   HOBTON,   P.   H.  TlMBEELAKE, 

C.  E.  Pembebton,  II.  L.  Sanfobd,  entomological  assistants. 
Beulah  M.  Boss,  preparator. 
J.  G.  Sandebb,  collaborator. 


Circular  No.  168.  Umua  April  it 

United  States  Department  of  Agriculture, 

BUREAU   OF   ENTOMOLOGY. 
L.  O.   HOWARD.   Entomologist  and   Chief  of  Bureau. 


SPRAYING   FOB  WHITE  FLIES  IN   FLORIDA. 

By  W.  W.  ITothebs,  Entomological    latUtant. 

Citrus  trees  in  Florida  are  subjed  to  injury  by  four  species  of 
white  flies  only  two  of  which,  however,  the  citrus  white  fly  (Aley- 
U.  &  II.)  and  the  cloudy-winged  white  fly  (Aleyrodes 
mtbifera  Berger),  do  sufficienl  damage  at  the  present  time  to  de- 
mand remedial  measures.  Of  the  two  species  considered  the  citrus 
white  fly  is  by  far  the  most  injurious. 

THE  CITRUS  WHITE  FLY. 

The  citrus  white  fly  is  an  introduced  pest,  having  been  brought 
to  (his  country  from  Asia  some  time  prior  to  L879.  Since  it<  intro- 
duction it  has  spread  over  the  entire  citrus  region  of  the  Mate  and 
westward  throughout  the  Gulf  region.  At  the  presenl  time  it  infests 
fully  60  per  cenl  of  the  groves  in  Florida.  It  occurs  on  some  10 
apecies  of  tree-,  and  shrubs,  the  most  important  hosts  being  the  China 
trees,  Cape   jessamine,   privet,  and   various  species  of  citrus.    Of 

native  plant-  the  only  two  which  have  been  reported   as  being  Seri- 
ously infested  are  the  prickly  ash  and  wild  persimmon. 

I.I  IK    BOSTOBl    AND    II  \l'.i  is. 

Th  completing  it-  life  cycle  the  citrus  white  fly  passes  through 
four  stages,  viz,  egg,  larva,  pupa,  and   adult. 

Th,-  egg. — To  the  unaided  eye  the  eggs  appear  as  minute  particles 
of  whitish  dust.  They  arc  deposited  on  the  underside  of  the  leaves. 
To  indicate  the  size  of  these  eggs  it  has  been  estimated  that  ih 
place. 1  end  to  end  would  measure  1  inch,  whereas  1  square  inch 
would  contain  about  35,164,  placed  side  by  aide.     When   examined 

1 


2  SPRAYING  FOR   WHITE   FLIES   IN   FLORIDA. 

under  a  magnifying  glass  they  resemble  kernels  of  wheat  in  shape 
and  appear  as  smooth,  polished,  greenish-yellow  objects.  After 
they  are  deposited,  from  10  to  12  days  are  required  for  the  eggs  to 
hatch. 

The  larva. — The  newly  hatched  larva  of  the  white  fly  is  active, 
resembling  that  of  a  scale  insect.  After  crawling  for  several  hours 
it  settles  on  the  underside  of  a  leaf,  inserts  its  beak,  and  begins  to 
take  nourishment  by  sucking  the  juices  of  the  plant.  To  reach 
the  pupal  stage  it  sheds  its  skin  three  times,  the  legs  being  reduced 
to  mere  rudiments  after  the  first  molt.  The  duration  of  the  larval 
stages  is  approximately  23  days. 

Hie  pupa. — The  pupa  closely  resembles  the  last-stage  larva,  but 
at  maturity  is  thicker,  more  rounded,  with  a  bright  red  spot  on  the 
back.  From  3  to  8  days  before  emergence  the  eyes  of  the  adult  be- 
come visible.  The  duration  of  the  pupal  stage  varies  from  13  days 
in  the  summer  to  a  maximum  of  304  days  during  the  fall,  winter, 
and  spring.  The  larvae  and  pupa?  secrete  honeydew,  which  drops  on 
the  leaves  and  fruit,  furnishing  nourishment  for  sooty  mold. 

The  adult. — The  winged  adults  emerge  from  the  pupal  cases,  which 
remain  attached  to  the  leaves.  They  collect  most  abundantly  on  the 
new  growth  and  there  they  deposit  their  eggs.  A  single  female  has 
been  known  to  deposit  as  many  as  250  eggs,  but  the  average  is  not 
more  than  150  for  each  individual.  The  average  life  of  the  adult 
is  10  days. 

Seasonal  history. — The  citrus  white  fly  passes  the  winter  in  the 
pupal  stage,  the  adults  of  the  first  brood  appearing  in  maximum 
numbers  in  March  or  early  April,  depending  upon  the  season  and 
location.  After  the  practical  disappearance  of  the  last  brood  there 
is  a  period  of  about  six  weeks  when  adults  are  scarce.  The  second 
flight,  or  brood,  of  adults  takes  place  in  June.  There  is  no  marked 
absence  of  adults  between  the  second  and  third  broods,  owing  to  the 
overlapping  of  these  broods.  The  third  brood  reaches  maturity  in 
August,  when  the  third  and  last  flight  of  adults  takes  place.  The 
eggs  deposited  by  this  third  brood  develop  to  the  pupal  condition 
and  thus  they  remain  on  the  leaves  until  the  following  spring.  The 
third  brood  is  by  far  the  most  numerous,  and  the  larva?  and  pupa? 
following  this  flight,  by  the  extraction  of  sap  and  the  excretion  of 
honeydew  upon  which  sooty  mold  grows,  cause  the  greatest  damage 
to  citrus  trees. 

THE  CLOUDY-WINGED  WHITE  FLY. 

The  cloudy-winged  white  fly  may  be  distinguished  from  the  citrus 
white  fly  as  follows:  The  eggs  of  the  former  are  dark  and  have  a 
reticulated  surface.    Those  of  the  citrus  white  fly  are  greenish  yellow 


sn:  !  i  OB    WHITE    nil-    in    ii  OBIDA.  .5 

iiml  smooth.  The  pupa  case  <>f  the  cloud]  \%  i mri-tl  white  fly  is  thin 
and  membranous  and  collapses  after  the  emergence  of  the  adult, 
while  thai  of  the  citrus  white  flj  retains  its  shape  indefinitely.  The 
adults  are  easily  distinguished;  the  cloudy  winged  white  fly  has  dark 
markings  <«n  it-  wings,  while  the  wings  of  the  citrus  white  fly  are 
pure  white.  The  broods  of  the  cloudy-winged  white  fly  appear  about 
a  month  later  than  those  <<(  the  citrus  white  fly. 

INJURY  FROM   WHITE  FLIES. 

The  injury  caused  by  the  citrus  and  cloudy  winged  while  flic-  i- 
much  greater  than  is  generally  supposed.  Tin-  damage  occasioned 
by  tin'  loss  of  sap  is  considerable  anil  1-  a  serious  'train  mi  the  tree, 
hut  i-  of  secondary  importance  to  the  damage  caused  by  the  sooty 

mold   which    follows  the  white  fly. 

The  sooty  mold  affects  both  the  fruit  ami  leaves,  blackening  the 
former  ami  covering  the  upper  surface  of  the  latter  with  a  dark- 
brown  coating  which  excludes  the  sunlight  anil  clogs  ami  checks  the 
growth.  The  reduction  in  yield  from  tin'  white  Hie-  ami  sooty  mold 
is  variously  estimated  to  he  from  25  to  50  per  cent. 

If  the  sooty  moli I  form-  a  coating  on  the  upper  half  of  the  orange, 
the  rind  underneath  it  may  remain  green  indefinitely,  while  the  lower 
half  of  the  fruit  becomes  well  colored.  The  retardation  of  ripening, 
delaying  as  it  does  in  some  cases  the  time  when  the  fruit  i-  market- 
able anil  materially  increasing  the  percentage  of  culls,  causes  further 
loss,  which  i-  very  conservatively  estimated  to  range  from  2  to  .">  per 
rent  of  the  value  of  the  crop. 

It  is  customary  to  dean  fruit  noticeably  affected  with  sooty  mold. 
The  process  of  cleaning  causes  many  mechanical  injuries  which  afford 
entrance  to  the  -pore-  of  the  blue  mold  with  its  resulting  decay. 

SPRAYING. 

White  Hies  may  he  controlled  in  two  ways:  (\)  By  subjecting  the 
infested  plant-  to  the  fume-  of  hydrocyanic-acid  gas,  or  (2)  by 
spraying  with  a  contact  insecticide.  The  latter  method  only  i-  con- 
sidered in  this  paper  and  has  the  advantage  of  being  comparatively 
inexpensive  and  adapted  to  grove  conditions  in  Florida. 

ait\i;  \  i  OS  FOB  -I'K  O  i\>.. 

Tn  spraying,  an  extension  rod,  varying  from  s  to  10  feet  in  length, 
should  be  supplied  with  each  line  of  hose,  the  length  depending  upon 
the  heighl  of  the  tree-.    This  roil  ma\  be  an  ordinary  bamboo  pole 

or  a  -mall  <:as  pipe.  The  former  i-  more  suitable  for  this  work  in 
that  it  i-  lighter  ami  more  easily  handled  after  becoming  wet. 


4  SPRAYING   FOR   WHITE   FLIES   IN   FLORIDA. 

* 

A  cut-off  should  always  be  inserted  between  the  extension  rod  and 
the  hose.  This  will  enable  the  operator  to  cut  off  the  spray  at  any 
time,  either  when  going  from  tree  to  tree  or  in  order  to  clean  out  the 
nozzle  should  it  become  clogged.  If  a  power  sprayer  is  used  it  is 
also  necessary  to  insert  a  cut-off  between  the  hose  and  pump,  which 
would  relieve  the  pressure  on  the  hose  in  case  of  a  break.  A  cut-off 
inserted  at  this  point  also  makes  it  possible  for  a  machine  to  be  fitted 
with  any  number  of  leads  of  hose  which  the  work  may  require. 

The  hose  should  be  from  three-eighths  to  one-half  inch  in  diameter, 
of  the  very  finest  quality,  and  able  to  withstand  such  pressure  as  the 
methods  of  application  may  require.  If  a  power  sprayer  is  used  the 
hose  should  be  a  good  quality  7-ply;  with  reasonable  care  this  will 
stand  up  for  a  season  under  150  or  170  pounds  pressure.  If  a  barrel 
pump  is  used,  4-ply  will  be  sufficient,  but  even  for  this  the  7-ply  is  to 
l)c  preferred  and  will  be  found  cheaper  in  the  long  run.  In  our  ex- 
perimental work  leads  of  hose  50  feet  in  length  have  been  found  more 
satisfactory  than  shorter  ones.  With  long  hose  both  mules  and 
machine  may  be  kept  out  of  range  of  the  spray.  Then,  too,  when 
using  two  leads  of  hose  it  will  be  possible,  if  the  hose  is  long,  to 
progress  uninterruptedly  on  both  sides  even  though  there  may  be  a 
tree  missing  in  one  row  or  the  other.  In  spraying  the  larger  trees 
long  hose  is  essential  in  order  that  the  sides  of  the  trees  away  from  the 
machine  may  be  reached. 

To  secure  satisfactory  results  the  application  should  be  thorough 
and  with  sufficient  force  to  break  up  the  liquid  into  a  fine  mist.  The 
kind  of  pump  to  be  used  should  be  governed  by  the  size  of  the  grove 
and  other  conditions.  A  barrel  pump  will  serve  every  purpose  if  the 
trees  are  low  and  only  a  small  amount  of  spraying  is  required.  For 
larger  operations  a  gasoline-power  outfit  will  give  better  satisfaction. 
For  Florida  such  an  outfit  should  be  light  in  weight,  with  6-inch  tires 
and  an  engine  of  not  less  than  two  and  one-half  horsepower.  To  keep 
the  machinery  free  from  sand  the  engine  should  be  provided  with 
canvas  curtains. 

To  obtain  satisfactory  results  it  is  necessary  to  have  the  proper 
equijunent  for  applying  the  insecticide.  Much  of  the  prejudice 
against  spraying  for  the  control  of  white  flies  arises  from  the  ineffi- 
cient results  due  to  improper  equipment. 

Since  the  insects  congregate  on  the  underside  of  the  leaves  the 
spray  should  always  be  directed  upward.  To  accomplish  this  one 
should  use  a  straight  nozzle  attached  to  an  elbow  which  makes  an 
angle  of  approximately  45  degrees  or.  better  still,  an  angle  nozzle 
which  will  not  get  entangled  in  the  foliage  and  branches.  A  nozzle 
which  emits  the  spray  in  the  form  of  a  cone  haying  an  angle  of  about 
90  degrees  has  been  found  to  be  very  efficient,  whereas  a  flat  or  solid 
stream  will  not  give  satisfactory  results. 


BPRAYING    FOB    w  1 1  III     I  I  1 1  B    in    PLOBIDA.  i> 

I n  i \\    PO   M'l'i  v    i  in    BPB  \  V. 

Tn  spraying  for  control  of  white  flies  the  method  of  application 
is  the  same  when  using  either  ;i  barrel  pump  or  :i  power  outfit. 

In  applying  the  spray  the  operator  should  begin  on  the  far  side 
dt"  the  tree  and  work  around  to  the  point  nearest  the  machine  I  he 
second  half  of  the  tree  should  be  handled  in  like  manner,  If  two 
operators  are  at  work  on  the  same  tree  they  should  l><>ih  l»'Lrm  :ii  t- 1 » < * 
point  farthest  from  the  machine  and  proceed  until  they  meet. 

Tin'  spray  should  be  applied  in  tin'  tree  in  a  systematic  way.  The 
operator  should  begin  at  the  base  ami  work  (<>  the  top,  inserting  the 
rod  among  the  branches  bo  a-  to  spray  the  center  of  the  tree.  Tin' 
entire  tree  may  be  thus  sprayed  in  sections,  tin'  operators  proceeding 
alternately  from  the  bottom  t<>  the  tup  and  from  the  top  t<>  the  bot- 

lom.    'In  prevent  kinks  from  appearing  in  tin-  hose  tl perator,  in 

moving  from  tree  i<>  tree,  should  never  make  a  complete  turn.  In 
case  kinks  appear  thej  should  be  immediately  taken  out  by  turning 
tin1  -pray  rod  ami  qoI  by  pulling  the  hose. 

BPB  \  V    M  i\  n  KB. 

It  i-  important  thai  tin-  insecticide  used  should  kill  all  the  inserts 
hit  by  the  spray.  Emulsions  of  various  heavy  mineral  oils  have 
been  found  to  give  the  |M.-t  satisfaction.  While  petroleum  fuel  oil, 
or  "crude  oil."  and  distillate,  or  <;a>  oil.  will  give  good  results,  yet 
the  paraffin  oil-,  known  also  a-  lubricating  oils,  having  a  specific 
gravity  of  from  24  to  28  Baume*  have  been  found  to  possess  cer- 
tain qualities  which  make  them  superior  as  base-  for  an  insecticide 
against  the  white  Hie-.  The  following  formula  ha-  given  highly 
satisfactory  results : 

Foumi  i  s   No.  1. 

Whale-oil   soap 8 pounds, or]  pallon. 

Paraffin  oil.  24"  or  28    Baume  2  gallons. 

Water 1  gallon. 

DIIU'   nonS   I  oi!  PR]  PARATIl 

Tn  preparing  the  stock  mixture  the  soap  should  be  put  into  a  re- 
ceptacle of  about  5  gallons'  capacity  and  the  oil  should  then  !><•  added 
very  slowly  while  the  mixture  i-  being  vigorously  stirred.  It  is 
important  that  the  oil  he  added  in  -mall  quantities  at  first  and  also 
that    the  stirring  he   sufficient    to  keep  the  oil   and   soap   in   the    form 

of  an  emulsion  after  each  addition  of  oil.    Thus  at   first   about  a 

pint  of  oil  should  he  added  to  the  -oap  and  the  mixture  stirred  until 
no  free  oil  appears.  As  the  amount  of  oil  i-  increased  it  should 
always  he  stirred  or  mixed  thoroughly  before  the  next  addition  is 


b  SPRAYING    FOB    WHITE   FLIES   IN    FLORIDA. 

made.  After  the  required  amount  of  oil  has  been  added  and  after 
free  oil  has  ceased  to  appear  on  top  of  the  soap,  the  water  is  slowly 
poured  in,  about  a  quart  at  a  time.  To  determine  whether  the  mix- 
ture will  form  a  perfect  emulsion  add  a  little  of  it  to  soft  water,  and 
if  no  oil  floats,  the  mixture  is  perfect  and  may  be  used  for  spraying. 
The  presence  of  floating  oil  indicates  an  imperfect  mixture  and 
results  from  adding  the  oil  too  suddenly  or  from  insufficient  stir- 
ring. This  condition  may  be  remedied  by  the  addition  of  more  soap, 
which  is  preferable  to  throwing  away  the  entire  mixture. 

For  spraying  orange  trees  u.se  1  gallon  of  the  stock  mixture  pre- 
pared as  just  described  to  50  gallons  of  water,  or  use  the  entire 
amount  to  make  200  gallons  of  spray  material.  This  dilution  con- 
tains approximately  1  per  cent  of  oil,  which  is  the  maximum  strength 
required  for  white  flies  and  the  purple  scale.  For  three-fourths  of 
1  per  cent  of  oil  add  1  gallon  of  the  stock  mixture  to  66  gallons  of 
water,  and  to  obtain  one-half  of  1  per  cent  add  1  gallon  of  the  stock 
mixture  to  100  gallons  of  water. 

Many  alterations  may  be  made  in  the  foregoing  formula.  The 
quantity  of  soap  will  depend  largely  upon  the  time  consumed  in 
adding  the  oil  and  the  amount  of  stirring  accompanying  this  process. 
The  amount  of  soap  is  lessened  if  the  stirring  is  uniform  and  if 
ample  time  is  taken  in  the  preparation.  Petroleum  fuel  oil,  or 
"crude  oil,"  and  distillate,  or  gas  oil,  may  be  used  instead  of  the 
paraffin  oil,  but  in  these  casas  a  mixture  of  about  twice  the  strength 
will  be  needed  to  kill  the  insects.  The  amount  of  water  is  unim- 
portant, since  the  emulsion  should  be  perfect  if  either  1  or  4  quarts 
be  added.  The  only  thing  to  be  remembered  is  that  the  diluted  spray 
should  contain  the  required  percentage  of  oil. 

The  following  formula  from  Farmers'  Bulletin  Xo.  172,  page  17, 
has  also  been  found  satisfactory : 

Formula  Xo.  2. 

Water    (  boiling) gallons..     5 

Distillate.'  28°  Baunie do 5 

Whale-oil    soap pounds..     1J 

DIRECTIONS    FOR    PREPARATION. 

Dissolve  the  soap  in  hot  water  and  add  the  distillate,  thoroughly 
emulsifying  by  means  of  a  pump  until  a  rather  heavy  creamy- 
yellowish  emulsion  is  produced.  For  use  against  "die  white  fly  dilute 
1  part  of  the  stock  emulsion  with  25  parts  of  water.  This  dilution 
will  contain  about  2  per  cent  of  the  oil. 

1  Tin'  term  "  distillate  "  ia  commonly  given  in  California  to  a  form  of  petroleum  widely 
ased  for  spraying  purposes. 


BPRAYING    FOR   whim    iiiis   i\    FLORIDA-  7 

PBOPRIS1  w:v    I  NSW  i  i<  IDH, 

There  are  Beveral  articles  on  the  market  under  the  bead  of  miscible 
oils  which  when  properly  applied  will  give  satisfactory  results. 
These,  however,  should  not  contain  sulphuric  Bcid,  rosin  oil,  or 
carbolic  acid. 

WHIN    TO   BPB  \Y. 

-  far  as  the  effed  of  various  insecticides  on  the  trees  and  fruit 
is  concerned  it  is  safe  to  spray  at  any  season  "f  the  year  except  dur- 
ing the  blooming  period.  It"  the  application  is  made  during  the 
winter,  it  will  be  found  much  more  convenient  t<>  Bpray  after  the 
removal  of  the  fruit.  The  insecticide  will  do  no  injury  to  the  fruit 
itself,  hut  its  presence  <>n  unwashed  fruit  may  prose  objectionable 
to  the  consumer.  It  can  also  be  applied  during  the  summer  or  rainy 
>ii,  l>ut  spring,  early  fall,  or  winter  applications  are  preferable 
in  that  the  benefice]  parasitic  fungi  are  not  affected  by  the  inseoti- 
i  ide  during  these  seasons. 

So  far  as  the  effect  on  the  various  stages  of  the  insects  i-  con- 
cerned spraying  may  be  done  at  any  tune.  The  white  fly  is  in  the 
tendered  larval  stages  about  two  week-  after  the  disappearance  of 
the  adults  of  the  first  brood,  ami  if  spraying  is  done  at  this  period 
the  insecticide  can  be  used  at  about  one  half  or  three-fourths  the 
usual  strength. 

The  grower  should  aim  to  keep  the  white  fly  below  the  point 
whore  it  will  do  serious  damage,  and  the  number  of  treatments  will 
depend  upon  the  thoroughness  of  the  work  and  the  abundance  of  the 
bisects  in  the  grove  at  the  time  of  spraying.  One  thorough  spray- 
ing is  much  more  effective  than  two  or  three  carelessly  applied. 

The  application  of  the  insect  icide  should  be  SO  timed  as  to  be  effec- 
tive in  killing  the  rust  mite  (Eriophyes  oleivorus  Ashm.)  and  scale 
insects  as  well  as  the  white  flies.  Experience  has  shown  that  two 
sprayings  are  sufficient  to  control  the  white  (lies.  One  of  these  can 
be  given  in  the  spring,  following  it  by  an  early  fall  application, 
or  one  can  he  given  during  midsummer  and  the  second  during  the 
winter  month-.  The  spring  and  summer  sprays  are  also  beneficial 
in  killing  the  rust  mite.  Sale  insects  frequently  gain  such  a  foot- 
hold as  to  demand  winter  treatment,  hut  in  some  instances  one  spray- 
ing a  year  has  produced  clean  fruit. 

SPRAYING   W   \m     iv-n   n    \M>    Tin-    BUBT    KITE. 

The  paraffin-oil  emulsion  spray  when  used  with  1  per  cent  of 
oil  will  kill  the  rust  mite  and  its  eir^s  and  also  the  purple  scale 
{Lipidosapfus    beckii    Newm.).      It    is    also    effective    when    used 


S  SPRAYING    FOR   WHITE   FLIES   IK   FLORIDA. 

against  the  young  of  the  Florida  red  or  "nail-head"  scale  (Chry- 
somphalus  aonidum  L.). 

EFFECT   OF   THE    OH    SPRAYS    ON    BENEFICIAL   FUNGI. 

The  experiments  so  far  conducted  indicate  that  the  oil  sprays  do 
not  possess  any  fungicidal  properties,  nor  do  they  affect  the  bene- 
ficial parasitic  fungi  in  the  least.  These  fungi  develop  during  the 
rainy  season,  while  the  scale  insects,  rust  mite,  and  white  flies  do 
their  greatest  damage  from  September  1  to  June  1.  The  fact  that 
these  sprays  are  applied  during  seasons  when  the  fungi  are  inactive 
is  evidence  in  favor  of  such  remedies  in  that  the  increase  of  the 
fungi  is  not  directly  affected. 

Approved : 

James  Wilson, 

Secretary  of  Agriculture. 
Washington,  D.  C,  January  IS,  1913. 


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